Father Remigijus Kuprys, 46, managed to extinguish the flames with the help of worshippers, but suffered facial burns, ABC News reports.
The attack occurred during the service on Thursday (local time) in the central Lithuanian town of Jonava, when a 42-year-old local resident sprayed Father Kuprys with the flammable liquid and set it ablaze with a cigarette lighter.
The motives of the assailant were unknown.
“We have reports that he had repeatedly disrupted masses and shouted weird statements. Investigators are deciding on psychiatric tests,” officer Mindaugas Juknys said.
Police said that the priest had been released from hospital after receiving treatment for his burns.
Lithuanian daily Lietuvos Rytas published a photograph of Father Kuprys with his face fully bandaged, with only the eyes and mouth visible.